Logging
RPM: Engine speed or revolutions per minute. N5x Engines have a maximum value of about 7000 rpm although maximum usable power is usually far below this maximum value. 　 Boost: This is the pressure, in PSI, in the charge pipe just before the throttle valve. Under ideal conditions the boost value will equal the boost set point value (see Target). The practical range of boost values is zero to about 20 psi. RPM affects the Turbos ability to generate high boost values. At low rpm (about < 2500 rpm) the exhaust flow is too low to adequately drive the compressor wheel to make high boost values. At very high RPM, the stock Turbo’s run far outside of their efficiency curve and hence capacity…. limiting the amount of boost available above 5800 RPM. The turbos ability to supply mass flow is also greatly affected by ambient air temperature and pressure (elevation). Raising either temperature or elevation decreases the mass airflow capability of the turbos. 　 Target: Target is the boost target or set point established by the JB4. It is generally a curve that peaks around 5500 rpm and falls off to either side of this rpm range. The various maps, pedal position, and internal logic will change the values and shape of the curve. 　 Typically when troubleshooting a car that is making less boost than expected you need to note whether the target is lower than expected thus resulting in less boost or if the target is appropriate but boost is falling below target. As troubleshooting for these symptoms are completely different. 　 In addition to the JB4 defined maps there is a map 6 available for diagnostics where the tuner can fill in the maximum boost targets by RPM under user adjustments. Although this generally is only used to make maps less powerful than what is already defined. Map 7 for example is about the highest boost targets that factory turbochargers will support. Many older cars will not be able to hit map 7 targets at higher RPM. ECU PSI: The ECU (Engine Control Unit) is just another name for the DME (Digital Motor Electronics) or engine computer. The ECU PSI is the value of boost the ECU thinks is the current boost value. With the JB4 this signal is altered by the piggyback to meet various tuning objectives. As boost follows target ECU PSI will generally follow DME BT (DME Boost Target). 　 DME BT: The DME BT displays the current boost set point for the DME (ECU). The stock DME BT psi range is about 0 - 9 psi but will vary based on engine speed, load and various temperatures and pressures. The DME BT value is read from the DME over the CANbus. The JB4 does not modify the DME BT as the value is calculated inside the DME computer. Flash Tunes, on the other hand, rewrite the tables inside the DME and generally do modify the DME BT. IAT: Intake Air Temperature is measured in the charge pipe just before the throttle valve and can be thought of as intake manifold temperature. It is measured by the TMAP sensor (Temperature Manifold Air Pressure) combination sensor…. Both boost and temperature in one physical sensor. Typical values for a car with the stock FMIC (Front Mount Inter Cooler), not running in boost, is 20 degrees above ambient. With the onset of a boost condition, the temperature will rise quickly as boost rises and also with the length of time of the pull. Values quickly go from the normal 20 degree rise above ambient to perhaps a 70 to 90 degree rise. The best upgraded FMIC will start out with only a 10 degree rise when not under boost and will limit the temperature rise to only about 25 degrees over a several gear pull. Also the lower the ambient temperature is the better the outlet temperatures will be. Meth/water injection is almost always injected prior to (upstream) of the TMAP sensor location and therefore, results in this value dropping as injection commences. With the nozzle sizes used today (CM 10, 12, 14), a typical IAT reading will drop about 30 degrees from the IAT starting value just prior to going WOT (Wide Open Throttle). IAT below ambient temperature is typical using meth/water injection. Reading is always displayed in Degrees F and is read from the left hand scale X 10. 　 Pedal: Gas pedal input. This is the position of the pedal under your right foot with a range of 0-100%. While using cruise control this value will always report zero. Throttle: Throttle blade position (0-100%). The throttle trend displays the position of the throttle in percent. The DME takes the pedal position signal (or if higher, cruise speed demand) to generate an engine load demand signal. The load demand signal is then used to index most of the internal variables in the DME. 　 Note that unlike a non turbo engine, the BMW boosted engine moves the throttle demand open much quicker than the pedal position demand and uses boost control to determine overall load and power above minimum power levels. Note: Corrective actions such as loss of traction control action or ECU PSI over DME BT or very low HPFP pressure can all cause the throttle to close…..without user input. 　 PWM: Stands for pulse width modulation but is also known as wastegate duty cycle. Represents the demand for the boost signal going to the vacuum control solenoid(s). The larger the signal the more vacuum is applied to the WG (Waste Gate…. exhaust gas bypass valve) control actuator and the harder the WG plug is forced onto the WG seat. The system is designed to "fail" in the WG open position so that the engine is not subjected to high boost conditions under a failure condition, such as a broken wire or faulty output. PWM does not actually control the WG position.... but rather the pressure ratio across the exhaust gas power turbine. The WG position actuator has a very weak spring in it and yet controls a WG plug with a large pressure drop across it at high engine rpms and boost levels. 　 At low to moderate WG demand signals, the vacuum applied to the WG actuator will totally close the WG plug. As rpm and boost build, at some point, the pressure drop across the WG plug will overcome the supplied vacuum force of the actuator and the WG plug will reopen, maintaining the established exhaust gas pressure ratio.... and indirectly, also the boost pressure ratio, with no further action by the DME. At high WG demand signal levels, the WG demand signal is great enough to maintain the WG plug on the WG seat, ensuring all gas flow passes though the power turbine. 　 During turbo spool up the JB4 will allow 100% PWM but under boost the cap is set to 86%. 　 FF: Short for "feed forward" or the fixed component of the PID boost control system. This is the starting point for boost control and the PID will then adjust PWM above or below this value as needed for fine tuning. The user adjustment variable FF / wastegate adaptation value (0 -150) scales the FF value and will adjust itself over time as part of the normal JB4 learning routines. DutyC: Dutycycle. This represents the DME's requested duty cycle. Which is the DME version of the JB4s PWM signal. Since the DME is no longer controlling boost this value has no meaning but is sometimes useful for diagnostics when troubleshooting boost issues that were not present before the JB4 was installed. 　 Ign1: Ignition Advance is the number of crank degrees BTDC (Before Top Dead Center) when the spark is turned on to ignite the fuel/air mixture in the cylinder. Generally higher engine loads/boost levels require less advance because the burning process progresses faster (less time to complete) under higher cylinder pressures. Higher engine rpm generally requires more ignition advance because there is less time for the cylinder pressure to build up before the piston starts it’s downward stroke. The displayed ignition advance value if for cylinder #1 but the DME can adjust timing on a cylinder by cylinder basis using an advanced knock sensor system with long term (octane detection) and short term (knock detection) trims analogous to a fuel trims. The displayed values can change a large amount under light to moderate loads….. more than 30 degrees on some engines. WOT (Wide Open Throttle) will result in a much narrower range of values….. usually dish shaped with values in the 10 to 13 degree range over the ends of the rpm band and a minimum valley value of about 6 - 8 degrees. Of more importance is watching out for sharp drops of more than 3 degrees in the engine high torque/power band…. typically in the > 4500 rpm range. Sharp drops of 3 degrees from one scan to the next indicate potential knock activity and are a general indication that the boost curve may be set too high for the available octane. Drops randomly throughout runs especially on pump grade fuels are expected but repeated drops in the same gear indicate an overly aggressive tune. Also note the DME will raise and lower advance as a function of normal mapping like during traction control events, gear changes, etc, and such drops are completely normal. 　 The JB4 uses this activity and the overall value of the ignition curve to calculate the Avg Ign (Average Ignition Retard) value. 　 Avg Ign: Average Ignition Retard. A JB4 calculated value with a range of 0 - 6 that represents the average amount of timing below the maximum possible curve over a short term window. Lower values indicate a higher overall ignition advance while higher values indicate a lower overall ignition curve. This calculation is used by the JB4 for evaluating octane content by both map 5 (auto learning) and map 3 (methanol injection). Values below about 1.5 result in full Map 3 or Map 5 scheduled boost levels. Values between about 1.5 and 6.0 result in lower and lower boost targets as an added safety feature for these two maps. As a general rule when using meth, race gas, or heavy E85 mixtures look for values below 2.0. When using pump gas expect values of 5 or higher. 　　 FuelEn: Fuel enrichment is a trend of the relative positive bias applied to the pre *** wideband O2 sensors. This bias allows the JB4 to effectively change the air/fuel ratio target. A higher bias means a richer targeted air/fuel ratio. And the DME will generally hit its air/fuel target provided the fuel trims are within range. 　 The amount of O2 bias applied can be adjusted by changing the "All Map AFR" table values under the "User Adjustment" Tab. Higher table values at a given rpm point will lower the AFR and richen up the mixture. 　 Note: The JB4 assumes this function will only be used on a factory flash. If using an aftermarket DME flash such as the JB4 back end flash this feature should be disabled by setting all values to 0 to avoid an overly rich condition. 　 Trims: Fuel trims (0-50). The Trims display shows what the STFT (Short Term Fuel Trim) signal is doing. Note this is only logged in N54 G5 ISO. N55 does not show fuel trims and instead has a meaningless parameter here. Values range from 0 up to 50 and unlike some of the other displayed values, the left hand scale range (Y value) must be set to 50 to see the entire range of this variable. A trim value of 50 means that the DME is adding 134% extra fuel..... while a trim value of 0 means that the DME is only supplying 92% of the normal fuel demand. An indicated value of 8 means that the DME is supplying its normally programed amount of fuel. The Y scale range can be set by going to the "Settings" Tab and changing the "X Scale 0 - 100" value. Note…. I know……. the Y scale value is adjusted by changing the X scale variable…. It is not a big deal…..only the difference between a boy or a girl. This signal can be quite variable but as long as it does not spend too much time pegged at 50 (maximum value) then all is well. If pinned at 50 for long parts of a run typically AFR will behind to lean out and tuning adjustments must be made to get fuel trims back within range. 　 This signal is used to calculate an automatically tuned variable FOL (Fuel Open Loop) or just OL (Open Loop) variable. See OL discussed later. 　 Meth: Methanol flow (0-100%). The meth display shows a voltage conversion of the JB4 0-5v #15 input. Typically this input is connected to a BMS supplied FSB system which is used by the JB4 to control the methanol pump and measure pump pressure and flow. This signal can also be read from a stand alone 0-5V flow sensor such as the one provided by Aquamist. 　 When using map 3 the JB4 will transition between a low and a high boost map as a function of "meth" and "avg ign". If using map 6 the JB4 will add the "Meth Boost Additive" to the map 6 values as a function of "meth" and "avg ign". 　 The user defined "Meth Flow Scaling" represents the minimum amount of flow to be considered "full flow". In the case of the FSB this value is 60. If methanol flow is half of the full flow value then the JB4 will target half way between its low and high map. 　 The field "Meth Boost Additive" determines how much boost the high map runs. With a maximum value of 80 representing approximately 20psi. Typically for pump gas operation a value of 40 should be used here (approx 17psi) while for race gas and/or E85 mixtures values of 60-80 are more appropriate. It is unlikely factory turbos will be able to hit targets higher than 65 so those are generally used only for aftermarket turbos. AFR: The AFR (Air Fuel Ratio in Lbs air/ Lbs gasoline fuel) trend displays the higher (leaner of the two banks of three cylinders.... cylinders 1>3 or cylinders 4>6. Typical values are 15:1 at light engine loads decreasing to around 12.5:1 under heavy engine loads and high rpm. Note: It is normal to have the AFR display 20:1 when car is coasting in gear or under a heave misfiring condition as the DME will cut off fuel to either the misfiring cylinder(s) or all cylinders if coasting. 　 　 FP L: Fuel pressure, low system. Pressure is read on the left hand scale X 10. Note this parameter is only logable in N54 G5 ISO. No other system logs this. Other systems will show oil temp in this location. Otherwise known as the in tank low pressure fuel pump. This value typically ranges from 55-70psi. If dropping below 50psi it indicates a problem with your low fuel pressure pump. Most often that problem is it needs to be augmented with an inline pump to keep up with the higher fuel demands required by ethanol usage. 　 FP H: Fuel pressure, high system. Otherwise known as the high pressure pump. Note all N54 include this and N55 can only log this if also equipped with the flex fuel connector. This value represents the voltage of the high pressure 0-5V sensor, where a value of 20 is 5v. Each unit of measure is roughly equal to 150psi. Typical values at full throttle are 10-14, or 1500 to 2100psi. Values of less than 900psi as full throttle indicate a fuel delivery problem and the JB4 will failsafe at 700psi at full throttle. Note when not at full throttle a typical value is 5 or 750psi. 　 Map: The currently selected map. Refer to the JB4 map guide for additional details. You can use the drop down menu to change maps here. 　 Gear: Currently selected gear. For manuals 0 means the car is out of gear or the clutch is depressed. 　 CPS: Short for "crank position sensor offset". This represents the number of degrees of offset being currently applied to the crank position sensor. Which is roughly equivalent to timing retard. Given the adaptive nature of the DME this feature is not often used unless directed by BMS technical support. 　 　 Clock: An internal JB4 variable used to keep track of various internal loops such as PID evaluations or ADC conversions. The value has no meaning to anyone other than BMS. FOL: Also read/copy this for information on FU(x) functions and remember to get the latest version (For the software you are actually running) as these functions can change as time goes on. These Notes are specific to each software version so remember to get a copy when you update your specific firmware. The following reference if for the N54 ISO software version 27.8.